1. Field of the Invention
The present invention relates to an inner rotor type motor.
2. Description of the Related Art
An inner rotor type motor has conventionally been used in many different applications. For example, the inner rotor type motor is used as a drive power source in office machines such as copy machines and combined machines. One example of such an inner rotor type motor includes a housing and a cover. Another example of an inner rotor type motor includes a sensor substrate which is attached to an electric insulation member of a stator and a magnetic sensor arranged to detect the magnetic pole position of a rotor is attached to the sensor substrate.
However, in the inner rotor type motor including the housing and the cover, a large number of work steps are necessary to confirm and adjust the positions of the housing and the cover in order to assure higher concentricity of the housing and the cover. In case where a single member press-formed to have a housing and a cover is used in place of the housing and the cover, there is a need to perform a complex deep drawing work. As a result, it is necessary to use expensive molds and to perform numerous work steps, which in turn increases the manufacturing cost.
In the inner rotor type motor including a sensor substrate provided with a magnetic sensor, the sensor substrate is fixed to an insulator attached to a stator core. The stator core has a laminated steel plate structure in which steel plates are laminated one above another. The lamination of the steel plates results in an accumulation of non-uniformity resulting from the manufacturing tolerances of the respective steel plates. As a consequence of this non-uniformity, the magnetic sensor must be greatly spaced apart from a rotor magnet in the axial direction to ensure that the laminated steel plate structure cannot come into contact with the rotor magnet. This may possibly reduce the detection accuracy of the rotational position of the rotor magnet.
Moreover, it is sometimes the case that the sensor substrate is deformed under the influence of pressure or heat applied thereto during the process of mounting electronic components. In this case, the magnetic sensor is spaced apart from the rotor magnet, which may possibly reduce the detection accuracy of the rotational position of the rotor magnet.